Red Hat build of MicroShift

Create a network policy allowing traffic to an application from a namespace

You can configure a policy that allows traffic to a pod with the label app=web from a particular namespace.

This configuration is useful in the following use cases:

Restrict traffic to a production database only to namespaces that have production workloads deployed.
Enable monitoring tools deployed to a particular namespace to scrape metrics from the current namespace.

If you log in with a user with the cluster-admin role, then you can create a network policy in any namespace in the cluster.

Prerequisites

Your cluster uses a network plugin that supports NetworkPolicy objects, such as the OVN-Kubernetes network plugin, with mode: NetworkPolicy set.
You installed the OpenShift CLI (oc).
You logged in to the cluster with a user with admin privileges.
You are working in the namespace that the network policy applies to.

Do not apply the network.openshift.io/policy-group: ingress label to custom namespace or projects. This label is Operator-managed and reserved for {product-title} networking functions. It should not be altered on system-created namespaces.

Using this label can result in intermittent network connectivity drops, unintended application of system NetworkPolicies resource, or configuration drift as the operator attempts to reconcile the state. For custom traffic grouping, always use unique, user-defined labels as shown in the following procedure.

Procedure

Create a policy that allows traffic from all pods in a particular namespaces with a label purpose=production. Save the YAML in the web-allow-prod.yaml file:
```
kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: web-allow-prod
  namespace: default
spec:
  podSelector:
    matchLabels:
      app: web
  policyTypes:
  - Ingress
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          purpose: production
```
where:

app

Applies the policy only to app:web pods in the default namespace.

purpose

Restricts traffic to only pods in namespaces that have the label purpose=production.
Apply the policy by entering the following command. Successful output lists the name of the policy object and the created status.
```
$ oc apply -f web-allow-prod.yaml
```

Verification

Start a web service in the default namespace by entering the following command:

$ oc run web --namespace=default --image=nginx --labels="app=web" --expose --port=80

Run the following command to create the prod namespace:
```
$ oc create namespace prod
```
Run the following command to label the prod namespace:
```
$ oc label namespace/prod purpose=production
```
Run the following command to create the dev namespace:
```
$ oc create namespace dev
```
Run the following command to label the dev namespace:
```
$ oc label namespace/dev purpose=testing
```
Run the following command to deploy an alpine image in the dev namespace and to start a shell:
```
$ oc run test-$RANDOM --namespace=dev --rm -i -t --image=alpine -- sh
```
Run the following command in the shell and observe the reason for the blocked request. For example, expected output states wget: download timed out.
```
# wget -qO- --timeout=2 http://web.default
```
Run the following command to deploy an alpine image in the prod namespace and start a shell:
```
$ oc run test-$RANDOM --namespace=prod --rm -i -t --image=alpine -- sh
```

Run the following command in the shell and observe that the request is allowed:

# wget -qO- --timeout=2 http://web.default

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>